The present invention is concerned with injection devices of the type that include a housing, a syringe received within the housing, the syringe having a bore in which a discharge piston having a bore is inserted, a drive element and an actuator for advancing the drive element so as to advance the discharge piston and discharge the contents of the syringe through its discharge nozzle.
These days, nearly everything is manufactured by machines. In some circumstances, machines are more reliable that manual labour and are they are very much less expensive. However, there is one faculty of a production line worker that, hitherto, machines have been unable to reproduce, and are unlikely to be able to do so for a long time to come. If a production line worker drops a part of the thing being manufactured, he may pick it up or he may select another from the parts bin. If a part is damaged, he may discard it. If the assembly operation he is undertaking is complex, he will ensure that the parts are properly aligned and assembled. He does all of these things because he is able to adapt to different circumstances and to use his judgment. Machines cannot.
During automated assembling of injection devices of the type mentioned above, there are a number of critical steps that need to be performed accurately and properly. Difficulties in performing these steps may arise from tight component tolerances or from the use of fragile components, such as glass hypodermic syringes. The particular assembly step with which the present invention is concerned is that of getting the drive element into the bore of the syringe, to which a number of challenges attach. Firstly, to act on the outer diameter of the syringe piston, it is necessary for the drive element to have a flat end face that is a close fit in the syringe bore. Secondly, this flat end face presents the risk that the drive element may jam onto the end of the syringe, particularly if there is any misalignment between the components. Thirdly, if automation is used to assemble the devices a jam between the drive element and the syringe could result in damage to the device or even breakage of the syringe. Finally, even if this operation is done by hand, it is often necessary to do it blind.